This invention relates to a signal reading control method for barcode scanner and particularly a control method that uses existing optical structure of a barcode scanner and provides an indication light which contains carrier frequency to project on an object, and receives confirmation of reflection signal frequency to make sure that the object is located within the reading range, and confirms the barcode scanner has been correctly pointing toward the barcode, then activates barcode reading operation.
Barcode scanner is widely used nowadays as a point-of-sales terminal to count consumers"" buying price at the counter. A cashier either takes the goods to scan in front of a barcode scanner, or takes a portable handheld barcode scanner to scan over the barcode of goods for reading the barcode image into the point-of-sale terminal for getting the price of each item and accumulated total amount at a display screen.
A conventional handheld barcode scanner starts scanning operation when a switch is pressed. One of such examples is disclosed in U.S. Pat. No. 5,821,520 which is a system capable of processing photoelectric signals for barcode scanners. The barcode scanner can read different reflection value from the barcode area and non-barcode area adjacent the barcode area. It includes a decoder for decoding input signals, a signal process circuit for processing signals output by the scanner and generates an input signal to feed into a decoder thereby to detect and delete the non-barcode area signals output by the scanner. The signal process circuit can generate a signal to input different barcode symbols into the decoder. The signal process circuit includes an eraser which has deleting function for deleting signals which have a shorter generation time period than a preset time period, one or two proportional calculator for calculating signal interval characteristics output by the scanner, and a second proportional calculator for calculating signal characteristics of non-barcode area output by the scanner. However the foregoing barcode scanner has disadvantages. First, when there is no object (barcode) presented in the effective reading range, the barcode scanner is still operational. The operation is meaningless and wastes electric power. Second, before the scanning lines are presented, there is no way of knowing if the scanner is correctly targeting the object.
There are other types of similar product being marketed. One of such products includes an additional reflective sensing element for detecting the object. Such an element usually can read at a distance of a few centimeter. A long distance barcode reader usually can read a distance of 15 cm, or 20 cm or even over 30 cm. Hence it is not desirable. Moreover, these types of reflective sensing element mostly are infrared light elements which have no object indication capability.
The primary object of this invention is to resolve aforesaid disadvantages, and to use the existing optical structure of the barcode scanner, and to provide an indication light which contains carrier frequency to project on an object, and to receive confirmation of the reflection signal frequency to make sure the object is located within the reading range, and to confirm the barcode scanner has been correctly pointing toward the barcode before starting barcode reading operation.
Another object of this invention is to correctly select the barcode to be read when targeting an object which has a plurality of barcodes printed thereon.
A further object of this invention is to use same optical structure and same signal receiving and amplifying circuit in the barcode scanner for the front stage detection operation and rear stage barcode reading operation such that detection positioning will be accurately attained and also to save power consumption.
To attain aforesaid objects, the signal reading control method according to this invention uses a laser element to generate light for detecting the object and indicating correct address of the barcode. When the button key of the barcode scanner is pressed, the scanner structure is not activated temporarily, at the same time a constant frequency oscillation wave is applied on a laser diode. The laser diode emits photo points in an oscillating manner at the same optical path of the barcode scanner. When a scanning object is being moved in the readable range, the light detect sensor of the barcode scanner will receive the reflection signal of same frequency added to the photo points. After signal amplification and wave forming process, a correct reflection signal will be obtained at the output pin. Hence once the signal frequency is confirmed to be same as the one emitted by the laser diode, it may be confirmed that the object has been entered in the readable range. In the mean time, the laser photo points have been projected on the scanning barcode, the barcode scanner will convert the laser diode to a constant current driving state, and activate the scanning structure to make the laser photo points become a scanning line for reading the barcode.